Objective: To evaluate the efficacy of inhaled corticosteroids (ICS) in patients with asthma based on changes in sputum eosinophil counts, through a review of relevant randomized controlled trials (RCTs).Methods: Studies were retrieved from MEDLINE, EMBASE, the SYSTEM FOR INFORMATION ON GREY LITERATURE, and the INSTITUTE FOR SCIENTIFIC INFORMATION from February 1, 2003 to February 1, 2013 based on a comprehensive search strategy. Articles were screened through two stages: title and abstract; and full-text screening. RCTs enrolling patients with asthma, testing an ICS intervention, and reporting outcomes on changes in sputum eosinophil counts pre- and post-intervention were included. Following screening, data extraction, and quality appraisal, a descriptive synthesis of trials was conducted.Results: The search strategy retrieved 447 articles, of which 66 articles underwent full-text screening, resulting in 37 RCTs that met the inclusion criteria for this review. The articles were stratified according to the type of ICS: budesonide, fluticasone propionate, ciclesonide, beclomethasone dipropionate, and mometasone. Across trials, 9 of 16 budesonide, 5 of 14 fluticasone propionate, 4 of 9 of nine ciclesonide, 2 of 4 beclomethasone dipropionate, and 1 of 2 mometasone interventions demonstrated a statistically significant (p < 0.05) reduction in sputum eosinophil counts.Conclusion: This study detected differences between ICS treatments however the clinical relevance is uncertain. There is insufficient evidence to suggest the superiority of one ICS treatment over another. Further research needs to be conducted to evaluate the relative impact of ICS products upon eosinophil counts, as well as in clarifying what quantitative level of change in baseline eosinophil counts is required to observe a change in symptom improvement and disease control.